(a) Field of the Invention
The present invention, which relates to hydraulic pumps, is particularly concerned with pumping devices having a plurality of pumping elements in a one-piece structure, thus allowing different modes of operation.
(b) Discussion of the Prior Art
There exist already several examples of one-piece pumping devices which include a plurality of pumping elements and which allow several modes of operation. Amongst the existing devices, mention must be made of the twin hydraulic pump which possesses two pumping elements, each driven by its own motor. It guarantees permanent operation, for all intents and purposes, in an installation using only one pump. The solution it provides to the requirement for permanent operation consists of including a pair of identical pumps in the same pump body, instead of one pump. The two halves of the device are operated alternately, the second element of the pair being provided to take over from the first if the latter, normally the only element operating, fails. This solution is excellent. The characteristics of each of the pumps are those of the single pump which the device replaces. Exceptionally, certain twin pumps have an additional possibility, which consists of operating both elements simultaneously. This type of operation is, nevertheless, exceptional, and normal operation of the device remains that of using only one of its elements, with the possibility of being backed up by an emergency element having the property of taking over automatically and instantly from the defective element. The very high dependability of the twin pump thus guarantees the reliability of the installation.
In a domestic or small factory environment, various types of pumping operations can arise: e.g., watering land, emptying reservoirs, removing flood water, etc. The characteristics of the pumps required for these various operations are not the same. For certain of these operations, such as watering, a high-pressure pump is required, whilst for other operations, such as pumping out flood water, a high flow-rate is required. Most of the time, however, the occasional nature of such applications does not justify the purchase of different types of equipment.